1. Field of the Invention
The present invention is directed to an assembly for footwear which requires adjustments by a wearer in order to maintain normal stability when the footwear is being worn. Such stability adjustments will result in the exercise and eventual strengthening of the foot and leg which does not occur when wearing conventional footwear. The footwear assembly includes an outer sole comprising a flexible material shell at least partially defining a hollow interior into which a plurality of substantially non-deformable, unconnected particles are movably retained. Applied foot pressure is transferred to the particles resulting in a change in the configuration of the outer sole and the creation of minor instabilities of the corresponding foot and leg, thereby requiring stability adjustments by the wearer.
2. Description of the Related Art
The field relating to shoes and/or soles for shoes is vast. Typically, known or conventional footwear include structural features directed towards creating a better support and comfortable fit as well as a stable grip of the outer sole with a supporting surface.
It is widely known that the exercise of walking barefoot on loose sand requires a greater effort than that of walking on firm ground. Therefore, walking barefoot on sand is excellent for the muscles of the feet, ankles and calves, and facilitates the expenditure of more calories. Accordingly, shoes have been produced that purportedly mimic walking on sand. However many shoes of this type have either a solid support or a support at least partially filled with air, wherein creation of the mimicked movement is derived from the bottom or outer portion of the sole. As a result, the corresponding foot is not truly going through the deformations provided by a substratum such as loose sand. In addition, conventional footwear of this type is generally incapable of exercising the foot, ankle, or leg of the wearer while standing still.
There have been numerous studies regarding the mechanics and of human locomotion on sand. In particular, a study done in 1998 by T. M. Lejuene, P. A. Willems and N. C. Heglund concludes that walking on sand requires 1.6-2.5 times more mechanical work than does walking on a hard surface at the same speed. Further, walking on sand requires 2.1-2.7 times more energy expenditure than does walking on a hard surface. The increase in expenditure of energy is due primarily to two factors: the mechanical work done on the sand, and a decrease in efficiency of positive work done by the muscles and tendons of the corresponding foot and leg.
Moreover, The Journal of Experimental Biology 201, 2071-2080 (1998), printed in Great Britain, and The Company of Biologists Limited 1998 JEB1432 indicates that barefoot walking on sand allows irregularities in the surface to move the tarsal, metatarsal, and toes (bones of the foot) relative to each other. The muscles of the foot and the intrinsic foot ligaments are therefore required to produce stabilization between bones. Muscles become fatigued as a consequence and ligaments are subject to increased strain. Should one desire to keep the muscles of the foot in good working order, walking barefoot, particularly on sand, is a good training method (Biomechanical Analysis of Fundamental Human Movement, Arthur E. Chapman).
Accordingly, there is a need in the construction and design of footwear which facilitates the strengthening of the foot, ankle, and lower leg of the wearer by providing at least a minimal amount of instability. As such, a proposed and improved footwear assembly would automatically or inherently require the wearer to make adjustments as foot pressure is applied to the proposed footwear to maintain stability in walking or standing. Such inherent adjustments by the wearer would thereby serve to effectively strengthen the foot, ankle, and lower leg. Such strengthening is at least partially due to the aforementioned “stability adjustments” being made on a substantially continuous basis as the various portions of the wearer's foot strikes the ground or other supporting surface while walking, standing, etc.
In addition, such a proposed footwear assembly should have structural features which allow the wearing thereof in a substantially normal fashion but which typically requires the stability adjustments of the wearer in a manner which does not significantly impede the overall balance and/or intended travel of the wearer over any type supporting surface.
Accordingly, the footwear assembly of the present invention provides a wearer with a totally different walking experience than that offered by known or conventional footwear. More specifically, the use of the proposed footwear assembly closely mimics the feeling of the wearer walking on loose sand. As such, the wearer may feel similar sensations as well as acquire the same benefits as if he/she were walking barefoot on loose sand. Moreover, the wearer of the proposed footwear assembly will be able to reap the above noted benefits, while having the bottom of the foot protected from cuts, lacerations, etc., which commonly occur when actually walking barefoot.